In general, a small speaker system has a difficulty in realizing a speaker system capable of satisfactory bass reproduction due to acoustic stiffness of a chamber of a speaker cabinet. Conventionally, in order to realize satisfactory bass reproduction in the small speaker system, there is a speaker system in which an activated carbon body is provided in the cabinet as a means of solving a problem of a bass reproduction limit which is determined based on a cabinet volume (see patent document 1, for example).
FIG. 9 is a cross-sectional view illustrating a main portion of a conventional speaker system. In FIG. 9, the speaker system comprises a cabinet 101, a woofer 102, activated carbon 103, a supporting member 104, a diaphragm 105, and an air tube 106. The woofer 102 is attached to the front of the cabinet 101. The activated carbon 103 in a form of a mass is disposed in the cabinet 101, and supported by a back face, a bottom face, an upper face, left and right side faces of the cabinet 101, as well as the supporting member 104. Note that small air holes for passing air are formed on an entire surface of the supporting member 104. The air tube 106 provided to the diaphragm 105 is operable to ventilate a space between the activated carbon 103 and the woofer 102.
Described next is an operation of the aforementioned speaker system. When an electric signal is applied to the woofer 102, a sound pressure is generated. A pressure in the cabinet 101 is varied by the sound pressure, and the diaphragm 105 is vibrated by the pressure which has been varied. Then, by the vibration of the diaphragm 105, a pressure in a chamber in which the activated carbon 103 is disposed is varied. The activated carbon 103, provided in the form of a mass, is supported by the supporting member 104 and the cabinet 101, and the small air holes are provided on the entire surface of the supporting member 104. Therefore, gas affected by the pressure variation caused by the vibration of the diaphragm 105 is physically adsorbed into the activated carbon 103, thereby suppressing the pressure variation in the cabinet 101.
As described above, in the conventional speaker system, the cabinet 101 operates equivalently to a large volume cabinet. Therefore, the speaker system having a small cabinet is able to realize satisfactory bass reproduction as if the speaker unit is provided in a large cabinet. Also, the air tube 106 is provided so as to prevent a pressure variation, caused by variations in ambient temperature or atmospheric pressure of the speaker system, in a space, including the activated carbon 103, which is enclosed by the diaphragm 105 and the cabinet 101. Note that the pressure variation caused by variations in ambient temperature or atmospheric pressure of the speaker system, occurs at a frequency lower than the bass reproduction limit of the woofer 102, the frequency being close to a direct current component.    [Patent document 1] Japanese Unexamined Patent Publication No. 60-500645